Many different gears are developed using many different types of valves. Elements for gear-disign are: how to get as less friction, how to get an independent inlet- / outlet-time, how to arrange steamregulation by cut-off.




slide valveThe slidevalve is one of the oldest gears. The fresh steam is pressing the valve against the chest to provide a steam-tight connection. Especially with overheated steam this gear gives a lot of wear on that surface.

The inlet and outlet have the same openingtime, therefore a short inlet-cut-off is not possible, it would cause a short outlet as well, Corliss valve-gear giving a lot of compression.

The inlet and outlet are combined in the same port, so there is a great risk of condensation



The corliss-gear is a very good and modern gear, capable of different timing of inlet and outlet. So a short cut-off can be combined with a long outlet-opening.The inlet and outlet are completely distinct so that there is less risk of condensation.

The gear uses tripvalves and the shutting is accomplished by a spring. The valves are cilindrical.


Paxman gear (Lentz-gear)

Paxman gear Paxman gear, cross sectionThis gear is especially designed for high-pressure and superheated steam.The valves are actuated by tappetrods from a  sideshaft. the valve-spindles are not packed but they are grooved to form a  labyrinth. In this way a very silent and almost frictional drive is achieved.

 The gear is used on uniflow-engines.

The gear was originally invented by mr Lentz, so it is known as the Lentz-gear as well,





Long D-valve

The (long) D-valve was invented at the end of the 18th century. The name is very obvious, it is D-shaped. The valve served both top and bottom half of the cilinder.
Clack valve




A clack-valve is one of the oldest known valves. The valve is also known as non-return valve. The valves were initially used in hand-operated kitchen-pumps. The valve is still used in many places.




Butterfly valve






The poppet-valvePoppet valve is the most common valve of all, used in allmodern internal combustion engines.


The piston-valve superseded the slidevalve when steam-pressure and temperature rose. The pistonvalve has less resistance and is better to lubricate.


corliss valve